Visible-Light-Drivenand Adaptable Liquid-CrystallineElastomer Actuators Containing Dynamically Exchangeable Boron Esterand Disulfide Linkages

A liquid-crystalline elastomer (LCE) containing dynamically exchangeable disulfide (−S–S−) and boron ester (BE) bonds (LCE_SS‑BE) was successfully prepared. The −S–S– linkages were introduced in the form of a reactive oligomer prepared via a thiol-acrylate Michael addition reaction with bis(2-hydroxyethyl) disulfide acrylate, while the BE linkages were incorporated via the visible-light-induced cross-linking of the oligomer with 4-((allyloxy)methyl)-2-(4-vinylphenyl)-1,3,2-dioxaborolane (AMVD). The monodomain LCE_SS‑BE (MLCE_SS‑BE) with ∼1 wt % AMVD promoted photothermal actuation under blue-light irradiation, resulting in a rise in its temperature of ∼147 °C and a decrease in its length of ∼42%. In addition, LCE_SS‑BE films exhibited reversible reprogrammability through two dynamic exchange reactions (DERs) involving either BE or −S–S– linkages. The BE linkages induced water-assisted healing through a hydration/dehydration DER under ambient conditions via a glue-free method, while the −S–S– linkages exhibited a UV-light-induced DER below the nematic-to-isotropic transition temperature, thus maintaining the nematic order during the DER. This approach represents a promising method for the preparation of MLCEs with light-induced actuation and multifunctionality involving reprogramming, reprocessing, and healing properties.